Long-lost star catalog discovered on Roman
statue
17 January 2005
"The constellations are one of our more enduring
intellectual properties, and in antiquity, they turned
the night sky into familiar territory. Dr. Schaefer's
clever and disciplined analysis of the oldest graphic
representation of the traditional Greek
constellations reveals unexpected roots of scientific
astronomy in a celebrated work of ancient art," said
E.C. Krupp, director of the Griffith Observatory in
Los Angeles.
An ancient mystery may have been solved by
Louisiana State University Associate Professor of
Physics and Astronomy Bradley E. Schaefer.
Schaefer has discovered that the long-lost star
catalog of Hipparchus, which dates back to 129
B.C., appears on a Roman statue called the
Farnese Atlas. Hipparchus was one of the greatest
astronomers of antiquity and his star catalog was
the first in the world, as well as the most influential.
The catalog was lost early in the Christian era,
perhaps in the fire at the great library in Alexandria.
Schaefer, who earned his doctorate from the
Massachusetts Institute of Technology in 1983,
specializes in astronomy and astrophysics. He has
long been interested in the history of astronomy
and has written extensively on the subject. He
began his examination of the Farnese Atlas statue
while conducting research on ancient constellation
lore.
Schaefer said that scientists have long held
Hipparchus in high regard for his work, which was
conducted between 140 B.C. and 125 B.C. He is
known for the discovery of the first nova and a
process called precession; a theory for the motions
of the sun and moon; top-quality planetary
observations; and the first-ever catalog of about
1,000 stars. Unfortunately, only one of Hipparchus'
books has survived to today: "Commentaries,"
which describes the constellation figures in detail.
The rest of his written work is known only through
The Farnese Atlas is a Roman statue, dating to the the references of later astronomers. For example,
second century, that depicts the Titan Atlas holding Schaefer said, Hipparchus' star catalog was
a sky globe on his shoulder. The statue, currently described in the work "Almagest" by the influential
housed in Italy, includes relief figures on the globe Greek astronomer and geographer Ptolemy, who
lived around A.D. 85 to A.D. 165.
depicting the ancient Greek constellations in fine
detail. Schaefer has discovered that the
The Farnese Atlas – roughly seven feet tall and
constellation figures on the Farnese Atlas are an
made of marble – is now in the Farnese Collection
accurate rendition of Hipparchus' star catalog.
According to Schaefer, the discovery will likely lead in the National Archaeological Museum in Naples,
to the solution of several long-debated questions. Italy. The statue's sky globe, which is 26 inches in
diameter, shows 41 Greek constellations, as well
as the celestial equator, tropics and ecliptic. Art
Indeed, Schaefer's discovery is already stirring
historians have concluded that the statue is a late
interest among those in the field of astronomy.
Roman copy of a Greek original. Schaefer said that
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the constellations are accurately depicted, so the
sculptor must have based his work on some
specific astronomical observations. Throughout the
last century, Schaefer explained, these
observations have been attributed to many
sources, but not Hipparchus.
Nevertheless, ancient star catalogs would have the
required accuracy. However, it is Hipparchus who
is known to have a star catalog created around the
correct time, 129 B.C., whereas the next catalog,
created by Ptolemy, came much too late, in A.D.
128.
Schaefer said that a number of facts led to the
conclusion that the statue's sky globe was based
on Hipparchus' catalog.
In addition, Schaefer said it is known that
Hipparchus constructed many sky globes based on
his star catalog. For instance, ancient coins depict
Hipparchus seated in front of a globe and Ptolemy
Precession, as discovered by Hipparchus, is a
writes explicitly of Hipparchus making such globes.
process whereby the stars and constellation figures Thus, Schaefer explained, a likely scenario is that
slowly move with respect to the celestial equator,
Hipparchus used his catalog to make an accurate
tropics and lines of constant right ascension. This globe, which was later copied exactly by a Greek
provides the key to dating the original observations, statue sculptor. Then, the Greek statue was later
Schaefer explained, because it means that
copied by a Roman sculptor.
investigators need only look on the sky globe to see
what date matches the constellation positions.
The constellations of the Farnese Atlas also contain
Thus, Schaefer traveled to Naples and made the
many specific details that point to Hipparchus as
first astronomical analysis of the constellation
the original observer. Schaefer made a comparison
positions.
between the Farnese Atlas and all ancient
constellation descriptions, including those of
For his analysis, Schaefer took his own pictures,
Ptolemy and other ancient astronomers and
because the photographic analysis requires
thinkers, such as Hipparchus, Aratus,
knowledge of the distance between globe and
Eratosthenes, Eudoxus and Homer. All ancient
camera. He measured a total of 70 positions on the sources other than Hipparchus have many and
globe and made a formal mathematical fit to find
major differences in their descriptions of the
the best date. Schaefer concluded that the best
constellations. However, the detailed comparison
date for the original observations is 125 B.C. He
shows Hipparchus' "Commentary" to have no
said that the normal margin of error in this result is differences and many unique similarities.
±55 years. In other words, Schaefer said, there is a
two-thirds chance that the real date was
Thus, the case for Hipparchus' lost star catalog
somewhere between 180 B.C. and 70 B.C.
appearing on the Farnese Atlas is based on:
Schaefer said that the date of 125 B.C. immediately
points to Hipparchus' circa-129 B.C. catalog as the
original observational source. Indeed, he said, all
previously proposed source candidates are
confidently eliminated because they come from
time periods that are either too early or too late.
The derived date of 125 B.C., which matches
Hipparchus and rejects all other candidates;
The fact that the accuracy of the sky globe requires
a star catalog, and only Hipparchus had created
one before A.D. 128;
The fact that Hipparchus is known to have
produced working sky globes from his catalog;
Positioning on the globe is another key indicator of The fact that only Hipparchus' description of the
the source, said Schaefer. The positioning of the
constellation figures matches the Farnese Atlas.
constellation figures on the Farnese Atlas has a
typical accuracy of 3.5 degrees. Schaefer said that Schaefer said that the discovery of Hipparchus' lost
such accuracy is essentially impossible to achieve star catalog on the Farnese Atlas could provide
by simple verbal descriptions (as found in the works answers to two long-standing questions that have
of other potential sources, such as Aratus or
been the source of heated debate: What did
Eudoxus) which are accurate to around 8 degrees. Hipparchus use as coordinates and what fraction of
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Hipparchus' star catalog made it into Ptolemy's
"Almagest?" Now, Schaefer said, with an accurate
representation of Hipparchus' catalog, researchers
can make exhaustive correlations between all
constellation figures on the Farnese Atlas and
those contained within "Almagest." But, Schaefer
said, perhaps the best part of the discovery is
"simply that we have recovered one of the most
famous known examples of lost ancient wisdom."
Schaefer announced his discovery at the American
Astronomical Society meeting in San Diego, Calif.
Source: Louisiana State University
APA citation: Long-lost star catalog discovered on Roman statue (2005, January 17) retrieved 17 June
2017 from https://phys.org/news/2005-01-long-lost-star-roman-statue.html
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